Electric-wave transmission



M. l. PUPIN AND E. H. ARMSTRONG. ELECTRIC WAVE TRANSMISSION.

APPLICATION FILED SEPT- 17. I915- 1,334,165.

' Patented Mar. 16, 1920.

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Patented Mar. 16, 1920;"

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' ITTOIMEB' M. l. PUPIN AND E. H. ARMSTRONG. v

ELECTRIC WAV,E TRANSMISSION. APPLICATION FILED SEPT-17, I915.

1,334,165. Patented Mar. 16,1920.

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ELECTRIC WAVE TRANSMISSION.

APPLICATION FILED SEPT- IL 1 915- I 1,334,165. Patented Mar, 16, 1920.

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vAPPLICA I'IQII FILED SEPT- 17. I915- Patented Mar. 16 I 6 SHEEIS-$HEEI 5.

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M. I. PUPIN AND E. H. ARMSTRONG. ELECTRIC WAVE-TRANSMISSION.

APPLICATION men sEifTQn. m5. P-atentedMar. 16,1920;

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- Referring to'the U ITED STATES, PATENT oiimoE.

micnann r;- PUPIN, or oRromr, CONNECTICUT, AND EDWIN H. ARMSTRONG, or YONKERS, NEW YORK. r

ELECTRIC-WAVE TRANSMISSION.

Specification of Letters Patent. Patented Mar. 16, 1920;

" Application filed September 17, 1915. Serial-No. 51,151.

To all whom it may concern:

Be it known that we, M CHAEL I. PUPIN, a citizen of the United States, residing in onnecticut, and EDWIN H. ARMSTRONG, a citizen of the United States, residing-in Yonkers, county of Westchester, State of New York, have invented certain new and. useful Improvements in Electric-Wave Transmissionsfand we do hereby declare the following to be'afull, clear, and exact description of the invention, such as will enable .others' skilled in the art to which it a'ppertains to make and use the same.

This invention relates to the production of a negative resistance reaction by means of a system of circuits containing a, local source of electrical power with meansjfor controlling it, and the application of this negative resistance reaction to the compensation' of the resistance reaction-of electrical conductors in order to make them responsive tosustained electrical waves of a predetermined frequency and not responsive to elec;

troinotive forces of a disturbingcharacter.

The apparatus described h'ere is, briefly stated, a new form of. resistance compensator operating in a generic sense similarly to the resistance compensator described by 'Michael I. Pupin in his copending applica- "tion, Serial No. 51,150 filed September 17,

diagrams which form a part of our specification, Figure 1v illustrates a system for producing the aforesaid negative resistance reaction, and Figs. 2 and 2 show'curves' of'its resistance and reactance -characteristicsforvarious frequencies. F 1g.

3 shows amethod of applying the resistance compensator to reduce the effective resistance of a conductor. Fig. 4; showsa system of magnifying the negative resistance reaction 7 produced by the system of Fig. 1 -bymeans pensator. Fig. '6 illustrates the method of of a magnifying shunt placed around the main conductor of thecompensator, and Fig.

5 illustrates the resistance and reactancecharacteristics obtained with a shunted com applying the shunted compensator to the tuning of a conductor. Fig; 7 represents a compensator consisting 'of a plurality of parts .connected in cascade system for the purpose of producing very large values of negative resistance. The characteristics of this system are illustratedby the curves of 't-he resistance compensator to a wireless an tenna.

.-In the particular arrangement illustrated in Fig. 1, an electrical valve 1 is coupled Fig. 8. Fig. 9 illustrates he application of with the main conductor 2, 3, 4, 5 on the inv .put side by meansof the circuit 6, 7 8, and on the output side by the circuit 9, 10, 11, 12.

The electrical valve illustrated hereisthe I well known vacuum tube containing a hot cathode 13 and a cold anode 9, between which a direct current flows, and a third electrode exciting circuit. By adjusting the constants of the exciting circuit 6, 7, 8, with r spect to the frequency of the incoming waves, the excitation of the valve is regu lated; The other circuit '13, 1'2, 15, 10, 9, contains an electrical battery 10 which maimtains a direct current between the hot cathode 13 and the cold anode 9. The incoming waves vary the electrical potential of the grid 14 and thereby 'thedirect current. This variation produces an electromotive force in x the main conductor 2, 3, 4, 5, by mutual induction between 4 and .12, whereby energyis.

transferred from the battery 10 to the main circuit. It is'thistransfer of energy which manifests itself through a reaction between 2, 5-, which has all the'properties. of a negative resistance reaction This second circuit with its battery 10 through ductorwill' therefore be referred to in this specification as the energizing circuit.

It will be seenthat in the arrangements described herein we have produced results by operations which are generically similar to which the electrical valve is connected to the main conthose ofjthe' induction motor resistance comcircuit fof the-induction I incoming waves and produces thereby the magnetic excitation, whereas the rotating secondar by its, electromagnetic reactions,

'itransfer's by expenditure of mechanical]Lenreaction; The." amount of the 'negative're-- sistance reaction produced bythe means em ployed in the present case depends upon the pensator described in the above mentioned- Pupinapplication, in which the; primary. 10o

tmotor receives the the frequency for which the exciting cuit when taken by itself is non-reactive.

relation of the constants of both the exciting and energizing circuits to the frequency of the incoming waves, and for the purpose of adjusting these constants, variable incuctances 7 and 12 and capacities 8 and 11 and a variable resistance 6 are employed. In other words, these circuits are capable of tuning.

- The effective resistance and the effective inductance of the system of Fig. 1 between the points 2 and 5 as measured by a Wheatstone bridge employing an'alternating electromotive force of suitable frequency, may be either as in Fig. 2 or Fig. 2", depending on the polarity of connection of the transformers 3, 7, and 4, 12. In Fig. 2 the maximum negative resistance in the main conductor is developed at a frequency below, and in Fig. 2 the maximum negative resistance is developed at a frequency above The negative resistance reaction in the main conductor 2, 5, is produced in the sys .stem of Fig. 1 by the following operations:

A current in the main conductor 2, 3, 4c, 5, induces in the circuit 6, 7 8, an electromotive force which charges the condenser 8 and the grid 14 connected to it. The charged grid produces a variation in the amplitude of the direct current flowing through the conductive channel 10, 15, 12, 13, 9. This current variation then induces an electromotive force in the main conductor 2, 3, 4, 5. The phase relation between the current in the main conductor and this electromotive force determines the reactions which are produced in the main conductor. If the electromotive force thus produced in the main conductor is so constituted in phase that one of its two components is in the same phase with the current in the main conducnegative resistance reaction may be varied,

and given any assigned limit, is discovered by connecting the terminals 2, 5, of the main conductor as represented in Fig. 1 into an arm of a Wheatstone bridge employing alternating electromotive force of suitable frequency and intensity. The curves illustrated by "'Figs. 2 and 2 are a result of a study ofthis kind. In these figures, the ordinates of curve R represent the effective resistance'and of .curve L,, the effective inductance between the terminals 2, 5, for

plication referred to.

various frequencies. It will be seen that these curves are in their main features, similar to those obtained with the induction motor compensator described in the previous ap- No exact general mathematical formulas can be given which will express the relation between the effective resistance and effective reactance of the main conductor and the electromagnetic constants of the various parts of the system and the impressed frequency. But an I experimental study by'means of a Wheatstone bridge enables one to construct easily an empirical formula for any particular case.

To apply this negative resistance reaction to the compensation of the resistance reaction of an electrical conductor, We proceed in the manner indicated in Fig. 3. Here 16, 17,18, is a conductor containing resistance, inductance and capacity and which is to be tuned to the frequency of an impressed simple harmonic electromotive force. The main conductor 2, 3, 4, 5, of the resistance compensator is placed in series with the conductor 16, 17, 18, and the circuit 6, 7, 8, adjusted to produce negative resistance between the points 2, 5, at the frequency for which the conductor 19 5, is to be made selective. The value of the negative resistance between 2 and 5 is adjusted to be slightly less than the positive resistance of the conductor 19, 2, so that the resultant effective resistance ofthe conductor 19, 5 is very much reduced forthe correct frequency. This has been explained at greater length in the previous application referred to. The negative resistance may be varied by adjusting the coupling between 4 and 12, or 3 and 7, or by varying the power of the valve to vary the local direct current, or by varying the Value of the resistance 6'. As the main function of the resistance 6 is to control the steepness of the resistance curves R- in Figs. 2 and 2 in the vicinity of their negative maxima and thereby vary the sharpness of tuning of the system, it is better to vary one of the couplings to obtain the required variation in negative resistance. The reactance of the main conductor is adjusted to zero for .the same frequency by means of the inductance 16 or the condenser 18.

For the right frequency, the conductor 19, 5, therefore, has zero reactance, and an effective resistance which is only a small fraction of the resistance added to it, but for all other frequencies, both the resistance and the reactance are relatively very large. The amount of positive resistance that can be added in this way is limited by the capacity of the resistance compensatorand by nothing else.

The arrangement of the present application lends itself to magnification of the resistance reaction by means of a shunt or 'by 30 ner as the arrangement of thePupin appliabove six times.

cation referred to, does.

This may be done by the arrangement represented by the diagram of Fig. 4:. In this arrangement which is the counterpart of the arrangement of Fig. 3 of "the previous applicatlon referred to above, a non-inductive shunt containing resistance 22 -is placed across-the conductor in which the negative resistance is produced. This conductor is provided with a series condenser 23 for the purpose of adjusting the effective reactance of the conductor. When the shunt positive resistance is made slightly greater than the shunted negative resistance, a large multiplication of the original negative resistance is obtained in the manner explained in the previous application. A shunt of 1200 ohms placed across the conductor having the characteristic of Fig. 2' ives a multiplication of he characteristic resistance and reactance curves are shown in Fig. 5.

To apply the shunted valve system for the purpose of compensating the resistance reaction of a conductor, we connect the conductor 20, 21, in series with the conductor 16, 17, 18, as illustrated in Fig. 6. The adjustments of resistance and reactance of the main conductor are made in the manner previously described for the simple resistance compensator.

Another method of producing a high negativeresistance is by means of a resistance compensator consisting of a plurallty of parts in cascade as depicted in Fig. 7 Two -parts are shown here, but any number of parts may be used to produce any required value of negative resistance reaction n the main conductor rov1d1ng due regard 1s pald to the proper ad uStment of the .phase of the mutual" inductance reaction between the energizing circuit and the main conductor. The characteristics of the particular arrangement of Fig. 7 are illustrated by the curves of Fig.- 8-. r

In the present application, as inthe previous application referred to,- the arrangement for producing negative resistance should preferably be such that the full value of the negative resistance cannot be produced instantaneously; that is, a certaindefinite length of time should elapse after h the arrival of'the initial impulse of a train of waves before the transient electrical state has passed into the stationary state in which the full maximum value of negative resistance is established. This length of time is determined by the durationof the transient stateof the. exciting circuit, and may be regulated by suitable adjustment of the resistance of this circuit which determines the rate of damping of its free oscillation.

To apply the resistance compensator to the reduction of atmospheric disturbances, we prefer to arrange the apparatus as in Fig. 9, in which a resistance compensator containing a plurality of electron dlscharge elements is arranged to produce in the antenna a high negative resistance reaction. The first part is connected to the antenna by means of a condenser 18 whichis located at the base of the antenna and is shunted by a resistance 26 which constitutes a leakage path .for electrostatic charges accumulating on the antenna. The particular advantage of the specified connection of 17 16 and 18 is a the shunt employed for magnifyingthe negative resistance reaction offers a means for shielding the induction motor from the direct effects of electrical impulses. We'find the same advantages are secured by the use of the shunt with the present form of re-- sistance compensator in the manner previ-v ously' described.

What. we claim is: Y I 1. Ina receiving system for electromagnetic ,waves, a receiving conductor into which is introduced a" resistance sufliciently high to screen the system effectively against disturbing electromagnetic waves impressed upon the conductor in combination with a resistance compensator consisting of anelectrical power source and means for 1 selectively transferring power from this source to the conductor by producing in the conductor a negative resistance reaction sufliciently large to compensate to any desirable "limit the losses due to the dissipative resistance introduced ductor.

2. In a wireless receiving system a wave conductor for the reception of electrical waves into which is introduced a resistance sufiiciently great'to make its resistance reaction large in comparison with its inductancereaction for all frequencies which are important in wireless Wave transmission. in combination with a resistance compensator consisting of an electrical power source and. controlling means excited by the incoming into the recelving conwaves for transferring power from' thepower source to the conductor to supply it with acompensating negative resistance, the resistance compensator being IBSPOIlSlVQ to a-susta1ned lmpressed electromotive force and substantially unresponsive to an in) pressed electromotive force of short duraresistance compensator being selectively responsive to a sustainedimpressed electromotive force and substantially unresponsive to an impressed electromotive force of short duration.

4:. A receiving system for electrical waves consisting of a receiving conductor with which has been associated a resistance-sufficiently large to screen the system effectively against disturbing electromagnetic waves impressed upon the antenna and a resistance compensator having an exciting circuit which is connected across a condenser in series with the receiving conductor so that the direct effect of electrical impulses of short duration on the compensator is greatly reduced. I

5. A receiving system for electrical Waves consisting of a receivlng conductor with which has been associated a resistance sufficiently large to screen the system effectively against disturbing electromagnetic waves impressed upon the antenna, a resistance compensator deriving its power from an electrical power source and connected to said conductor and a magnifying shunt across the said compensator containing a resistance of such value that the resultant negative resistance reaction of the combined circuits will be greater than the original negative resistance reaction to magnify the negative resistance reaction introduced into the main conductor and to shield the compensator from the direct effect of electrical impulses.

6. A resistance compensator consisting of a plurality of parts connected in cascade each part having an exciting circuit and an energizing circuit with an electrical power source, the exciting circuit of the first part being connected to a wave conductor,* and the energizing circuit of each part being connected to the exciting circuit of the succeeding part, except the last part, the energizing circuit of which is connected to the wave conductor, and in which at least one of the excitingcircuits is tuned, whereby there is selectively imparted to the wave conductor a high negative resistance reaction.

7. A resistance compensator consisting of a plurality of parts connected in cascade each part having an exciting circuit and an energizing circuit with an electrical power source, the excltmg circult of the first part being connected to a wave conductor, and

the energization circuit of each part being connected to the exciting circuit of the succeeding part, except the-last part, the energizing circuit of which is connected to the wave conductor, and in which at least one of the exciting circuits is tuned, and one of them having the characteristic that impulses imparted to it produce their full exciting effect after a predetermined time interval only. i

8. A receiving conductor into which has been introduced a resistance sufficiently high to make its resistance reaction large as compared with its inductance reaction for all wave transmission in combination with a v 

